"His Son is the image of the invisible God." Here "image" does not mean a representation of something that is visible. Instead, "image" here means that by knowing the Son, we learn what God the Father is like. (See: [[rc://en/ta/man/jit/figs-metaphor]])
The expression "firstborn" does not refer to when Jesus was born. Instead, it refers to his position as the eternal Son of God the Father. In this sense, "firstborn" is a metaphor meaning "most important." Jesus is the most important and the unique Son of God. Alternate translation: "God's Son, the most important one over all creation" (See: [[rc://en/ta/man/jit/figs-metaphor]])